Optical Fibers Need Critical Process Control

Optical fiber is designed to guide or transmit light in applications where illumination is needed for a target or area where light is not easily available. For instance, optical fiber can bring natural light into dark or recessed areas of buildings and has many uses in architectural, medical, inspection, and other types of applications.

Kelly Downey, M.S.E.E., Opto 22

01/01/2008

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Optical fiber is designed to guide or transmit light in applications where illumination is needed for a target or area where light is not easily available. For instance, optical fiber can bring natural light into dark or recessed areas of buildings and has many uses in architectural, medical, inspection, and other types of applications.

Southern-California-based Lumenyte International Corporation specializes in fiber optic lighting solutions for original equipment manufacturers and a number of industrial, architectural, and transportation-related industries. Over its 26-year history of innovation, Lumenyte has provided sophisticated and energy efficient plastic fiber optic lighting systems to a worldwide customer base. The company has also promoted use of fiber optic lighting beyond simple decorative and aesthetic uses to more utilitarian functions, including several patents for technologies such as linear emitting fiber optics (LEF), the only functional sidelight fiber optic currently available.

Today, Lumenyte boasts an impressive roster of clients, many of whom chose Lumenyte systems for their design flexibility, ease of maintenance, and in particular, their energy conservation qualities. Lumenyte facilities and production operations manager Scott Dill says that many of the companies that are now sourcing fiber optic solutions do so as part of a larger concerted, company-wide energy conservation (or “green”) efforts. They recognize fiber optics, when coupled with energy efficient light sources, as a viable low energy lighting option. This new industry has the potential to save considerable amounts of energy throughout the world.

Lumenyte has branched into a broad and diverse assortment of application areas, such as customized architecture, and has also found great success in developing solutions in the military and homeland security sectors. Examples include the development of a variety of self-illuminating telescoping search and inspection mirrors, LEF lighting for US Navy ships and aircraft carriers, and the security illumination mat system (SIMS), which uses fiber-optic technology to provide a portable under vehicle inspection system to detect the presence of explosive devices.

PACs in control

Lumenyte is currently using Opto 22 Snap PAC (programmable automation controller) systems to control and monitor a host of equipment used in the manufacturing of its plastic optical fibers. This equipment includes a large stainless steel casting chamber, 56 ft long with a diameter of 16 in. What goes on inside the casting chamber is classified, as much of the technology is proprietary and developed in-house.

“This chamber has what we refer to as a 'hot side' and a 'cool side', and it is one of the key pieces of manufacturing equipment used to produce our optical fiber,” says Dill. “We use the Snap PAC system in many phases of a very complicated process that relies on repeated heating and cooling with the application and accurate measurement of very precise temperatures, flows, and pressure.”

For example, Opto 22 Snap analog I/O modules and an M4 RTU controller monitor the levels, flows, temperatures, and pressures in a process using more than 35 various sensor inputs. The Opto 22 controller regulates over 50 ball valves that open and close in various sequences and percentages so the sequences, flows, temperatures, and pressures are accurately maintained at specified parameters. Also monitored are flow meters, which send data to the controller to ensure that the flow rates calculated and set in the Opto 22 control program are maintained.

Lumenyte also uses the Snap PAC to regulate nitrogen delivery equipment, controlling the flow of liquid from a 3,000 gal. nitrogen holding tank to a liquid nitrogen cooling system. The cooling system plays a critical role during optical fiber production processes. Inlet pipes and valves are regulated to divert liquid nitrogen through different parts of the cooling apparatus to provide necessary flow and cooling effect.

“The casting chamber's heating elements are also controlled by the Snap PAC system, so as water is added, we initiate a progressive heating process to get the water temperature properly elevated and then maintained,” says Dill. “Changing this cool environment to a very warm one is a critical part of our process.”

Down at device level

To execute this process, the Snap PAC interfaces to analog and digital I/O modules. In turn, the modules connect to the various valves, flow meters, and circulation and metering pumps' drives and motors. The Opto 22 strategy executes all the logic used to control all of the equipment for the cooling process, such as drawing water out of large tanks and delivering it to the chamber. As the strategy executes, specified amounts of water are introduced into the process until optimal temperatures are reached for that step. Once complete, additional changes are initiated, including heating to a new higher temperature level.

Lumenyte's mix of flow and pressure sensors, type T and J thermocouples, and resistance temperature detectors (RTDs) are all wired back to the controller via Snap analog I/O modules and the data they deliver then becomes part of the executing control strategy. Using the Optodisplay runtime HMI, all aspects of the process are closely monitored to ensure that they meet strict parameters defined in the strategy by Lumenyte operators. The flexible Optodisplay HMI makes it easy for operators to preset many different parameters for many different production requirements. Upon completion of the process, the controller initiates a complete shutdown returning everything to its original state so the product can be removed for further processing.

Upgrades in progress

Lumenyte is now in the process of upgrading its Opto 22 serial-based mistic (generation 1) Snap PAC system with a newer (generation 3) Snap PAC S-based system. In doing so, Lumenyte's team has had to migrate all of their control strategies—a task they've found to be much easier than expected. The Snap PAC S1 has an RS-485 serial port that Lumenyte uses to connect to all of their external I/O—thereby saving the trouble of deploying new I/O and also having to rewire much of the control architecture. At the same time, PAC Control Professional, the programming environment for the Snap PAC System, supports the mistic I/O serial communications protocol and command set, allowing Lumenyte to migrate to the newer software and import their existing control strategies.

“Readdressing these strategies is something that we were going to do anyway,” says Dill. “But PAC-based control has made importing them fairly painless and there've only been a few [strategy] errors. The PAC platform gives you a highly intuitive interface that reflects your understanding of what's happening with your process and the software goes well with the solid Opto control system. Plus, it's easy to learn, just as flexible, and more straightforward than ladder logic. The easier learning curve has allowed us to use Opto 22 as an effective control system and Opto 22 customer support has been the best I've ever encountered.”

As Lumenyte maintains its leadership in developing fiber optic solutions, the company will continue to rely on its partnership with Opto 22, and the superior control, monitoring and data acquisition interfaces the company is able to provide for Lumenyte's many complex manufacturing processes. ce

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